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A chemical reaction(1) in genes(2) that control breast cancer(3) provides a molecular(4) clock that could one day help researchers(5) more accurately(6) determine a woman’s risk for developing breast cancer and provide a new approach for treatment(7), UT Southwestern Medical Center researchers have found.

In a study published in today’s issue of Cancer(8) Epidemiology(9) Biomarkers(10) & Prevention(11), scientists from UT Southwestern show that the chemical process(12), called methylation(13), is strongly correlated with(14) breast-cancer risk and with precancerous changes(15) in the breast cells(16).

The researchers determined that methylation acts as a type of biological(17) clock, indicating how many times a cell has divided(18). This information could aid researchers in determining an individual’s cancer risk.

“The more a cell has divided, the greater the risk for cancer,” said Dr. David Euhus, professor(19) of surgical oncology(20). “Monitoring methylation levels could give researchers a way of seeing how often cells have divided and where a woman stands on that clock. Once the clock reaches a certain hour, breast cancer is more likely to ensue(21).”

During methylation, small molecules(22) called methyl groups(23) attach themselves to a gene and turn off(24), or “silence(25),” the gene.

Previous studies by Dr. Euhus have shown that apparently(26) normal breast cells from women with breast cancer had increased methylation of a tumor-suppressor gene(27) called RASSF1A(28).

In the current study, Dr. Euhus wanted to see if methylation of RASSF1A and other genes increased over time during the years when the ovaries(29) are actively secreting(30) estrogen(31) and progesterone(32) each month.